This invention relates generally to rotary cutters and particularly to cutters such as milling cutters or planing heads in which the cutting elements are disposed helically about the body of the cutter in the direction of the longitudinal axis of rotation of the head. Usually the cutting elements are disposed in helical slots in such a way that they can be vertically adjusted within the slot and so that they can be replaced or removed for sharpening purposes, repositioning, or the like. It is known to seat the cutters by means of wedging devices, positive stops, or screw means in the slots and cooperable serrations cut in the cutter and in one of side walls of the helical slots which intermesh. In this way the cutters are maintained in a fixed position relative to the head. Until the advance described by the present invention, there have been no known cutting heads which use cutters which can be removed or repositioned without subjecting the head, and consequentially the corresponding machine, to a great deal of down time (some designs require the head to be out of service for as much as 3 to 4 days) because of the long trial and error process using special tools which is required to reposition all the cutters at the same precise location with respect to the head so that all the cutters describe the same diameter as the head rotates.